mus: The window server needs to be able to write to the clipboard.

services/ui/ws/window_server.cc

Index: services/ui/ws/window_server.cc
diff --git a/services/ui/ws/window_server.cc b/services/ui/ws/window_server.cc
index 92aa4ae19d65c1d2b631ff3ec2132de0d80922db..8403378fe7ed0275a8be8fa4e1d41901baadf821 100644
--- a/services/ui/ws/window_server.cc
+++ b/services/ui/ws/window_server.cc
@@ -242,6 +242,12 @@ void WindowServer::OnFirstWindowManagerWindowTreeFactoryReady() {
   delegate_->CreateDefaultDisplays();
 }
 
+ui::clipboard::ClipboardImpl* WindowServer::GetClipboardForUser(
+    const UserId& user_id) {
+  DCHECK_GT(clipboard_map_.count(user_id), 0u);
+  return clipboard_map_[user_id].get();
+}
+
 UserActivityMonitor* WindowServer::GetUserActivityMonitorForUser(
     const UserId& user_id) {
   DCHECK_GT(activity_monitor_map_.count(user_id), 0u);
@@ -769,10 +775,12 @@ void WindowServer::OnActiveUserIdChanged(const UserId& previously_active_id,
 
 void WindowServer::OnUserIdAdded(const UserId& id) {
   activity_monitor_map_[id] = base::MakeUnique<UserActivityMonitor>(nullptr);
+  clipboard_map_[id] = base::MakeUnique<clipboard::ClipboardImpl>();
 }
 
 void WindowServer::OnUserIdRemoved(const UserId& id) {
   activity_monitor_map_.erase(id);
+  clipboard_map_.erase(id);
 }
 
 }  // namespace ws